The present invention relates to RJ jacks having means for preventing damage to the contacts of the jacks from insertion of non-complementary plugs and, more particularly, to RJ45 jacks having means for preventing damage to the contacts of the RJ45 jacks from insertion of RJ 11 plugs.
An RJ11 connector comprises a six-contact plug and corresponding jack commonly used to connect a communications device such as a telephone, facsimile machine or modem to a telephone line. An RJ45 connector, which is somewhat wider than the RJ11 connector includes eight contacts and is commonly used for Ethernet local area network (LAN) connections.
Referring to FIGS. 1A and 1B there are shown diagrammatic bottom and elevation views, respectively, of an RJ11 plug 10, and referring to FIGS. 2A and 2B there are shown diagrammatic bottom and elevation views, respectively, of an RJ45 jack 12 in insertion alignment with the RJ-11 plug of FIGS. 1A and 1B, with FIG. 2A only showing the contacts 14 of the RJ45 jack 12. The RJ11 plug 11 includes six contact fingers 16 for mating with six contact fingers of an RJ11 jack (not shown). The RJ45 jack 12 includes a housing 18 having an interior chamber 20 with an opening through the front wall through which an RJ45 plug 22 (FIG. 3) may be received into the interior chamber 20. Eight resilient contact fingers 14 are arranged in the chamber 20. The spacing between the jack contact fingers 14 is equal to the spacing of corresponding contacts 26 in the RJ45 plug 22 (FIG. 3).
RJ11 and RJ45 receptacles are often found close to one another, for example, as side-by-side wall jacks in office or other commercial or industrial environments, on computers, on adapters, etc. This proximity can lead to damage to the contacts of the RJ45 jacks.
This is because the RJ11 and RJ45 designs are dimensionally similar, allowing the smaller RJ11 to feign proper mating without any tactile sense of the connection being forced. The results of this all-too-common error are at least damaging and can totally destroy a jack's electrical integrity by permanently crushing its outermost contact fingers.
The root of the problem is that the RJ11 plug is essentially a narrower, six contact version of the eight contact RJ45. Engagement dimensions and contact pitch are common to both. However, the narrower contact region of the RJ11 plug places its body's wide sidewalls 24 (FIG. 1A) directly in line with the outboard contacts 14a and 14h of the RJ45 jack 12 (FIG. 2A). These contacts 14a and 14h are designed to hook into relief slots on a mating plug, so the solid sidewalls 22 of the RJ11 tend to crush them during a mating attempt.
Contact force between plug contacts and jack fingers of RJ series connectors is generated by deflecting the inclined, cantilevered, spring fingers of the jack downward as a plug is inserted. For a plug to produce this force, it must enter the jack along a line of action parallel to the planes of the jack's floor and top. Further, the overall height of the plug's body must be only slightly less than the distance between the jack's top and floor so that the top surface of the plug is able to bed against the roof of the jack, thereby insuring that the contacts maintain a fixed height above the jack floor as the upwardly directed force of the fingers grows to more than 100 gms per contact during mating.
As seen in FIG. 3, the contacts 26 of an RJ45 plug 22 are recessed in grooves 28 that keep them typically 0.020″ above the base plane of the plug's shell. As shown in FIG. 3, so long as each contact 26 coincides with its corresponding groove 28, proper mating geometry is maintained. However, if, as seen in FIG. 4, a narrower RJ11 plug 10 is pushed into an RJ45 jack opening 20, no contact grooves 28 are presented to receive the outermost fingers 14a and 14h of the RJ45 jack 12; instead, the shoulders 24 of the RJ11 plug 10 engage the outer fingers 14a, 14h and, as a result, the fingers are driven down close to the plane of the jack's floor, permanently deforming them.
As used herein, the term “complementary plug” means a plug of the same RJ series as an RJ jack and the term “non-complementary plug” means a plug of a different RJ series than an RJ jack.